Meshing rotary piston machine with an internal shaft

ABSTRACT

The invention relates to fluid pressure motors and pumps of the type having a gerotor displacement mechanism and an axial type of valve. The casing has inlet and outlet ports and a speed and load control port. The rotary valve has first and second sets of alternately arranged passages with one set having the usual constant fluid communication with the casing outlet port. The other set of valve passages includes some passages in constant fluid communication with the casing inlet port and at least one passage in constant fluid communication with the casing control port. A change over unit has a fluid supply inlet, a fluid exhaust outlet and a control outlet connected to the casing control port referred to above. The change over unit has means for selectively and alternately connecting the control port to the supply inlet and exhaust outlet thereof.

Giversen Dec. 11, 1973 MESHING ROTARY PISTON MACHINE WITH AN INTERNALSHAFT [75] Inventor: Svend Giversen,Sonderborg,

Denmark [73] Assignee: Danioss A/S, Nordberg, Denmark [22] Filed: July14, 1972 [21] Appl. No.: 271,810

[30] Foreign Application Priority Data Primary ExaminerCarlton R. CroyleAssistant Examiner-John J. Vralblik Attorney-Wayne B. Easton [57]ABSTRACT The invention relates to fluid pressure motors and pumps of thetype having a gerotor displacement mechanism and an axial type of valve.The casing has inlet and outlet ports and a speed and load control port.The rotary valve has first and second sets of al ternately arrangedpassages with one set having the usual constant fluid communication withthe casing outlet port. The other set of'valve passages includes somepassages in constant fluid communication with the casing inlet port andat least one passage in constant fluid communication with the casingcontrol port. A change over unit has a fluid supply inlet, a fluidexhaust outlet and a control outlet connected to the casing control portreferred to above. The change over unit has means for selectively andalternately connecting the control port to the supply inlet and exhaustoutlet thereof.

8 Claims, 5 Drawing Figures isconnected to and rotates with the firsttoothed element and containsvalve openings leading to the displacementchambers, the number of which openings is equal to the number of teethon this toothed element, and a second part of which is connected to androtates with the second toothed element and contains valve openingsconnectedrespectively to a pressure side first union and to alowpressure of intake side second union, the number of these openingsbeing equal to twice the number of teeth on this toothed element.

In one known machine of this kind the toothed elements not only actasrotary pistons but also effect a reduction. Machines of this kindaretherefore particularly well suited for slow operation. Engines have ahigh torque and pumpshave high delivery capacities.

The objects of the present invention is to provide a rotary pistonmachine of the initially stated kind which hasmore than onetransmissionratio.

According to the invention, this object is achieved by the use of asecond toothed element. having an even number of teeth and by theprovision of a change over device by means or which each second or eachfourth of the valve openings in the-second part ofthe distributingvalveis optionally connectible to one of the unions, preferably the pressureside first union, and the intermediate valve openings are connectible tothe other unlOll.

When each second opening is connected to the same union, the machineoperates in the normal manner. If however, only each fourth valveopening is connected to one of the unions whilst the three intermediatevalve openings are assigned to the other union, a new kind of operationis surprisingly achieved.'lf an engine is operated under constantexternal conditions (pressure-level and throughput), then it operates atapproximately twice thespeed'and with half of the torque. Thetransmission varies inthe ratio 1 2. If the machine in question is avehicleengine, its speed can be changed without the aid of a change'overgear. The same applies in the operation of axpump.

It is particularly advantageous if the toothed wheel constitutes thesecond toothed element and has six teeth. With thisarrangement, only onechamber is connected to the pressure side each time. This chamber islocated in the middle of the three otherwise effective pressurechambers, so that the chamber having the greatesteffective componentinfluences the rotation of the toothed wheel. The same applies when thisone chamber is connected to the low-pressure or intake side.

A simple construction is that in which each fourth valve opening inwthesecond part of the distributing remaining valveiopenings, as required,to one or other of the unions. In this arrangement, only each fourthvalve opening requires to be changed over. i

In a preferred embodiment the valve openings in the second part of thedistributing valve take the form of axial grooves in the periphery of arotary slide, three axially staggered annular grooves are formed in theperiphery of the rotary slide, the first of these being connected to oneof the unions and being located on one side of the axial grooves, thesecond being connected to the other union and being located on the otherside of the axial grooves and the third being connected to the changeover device and being located on that side of the second annular grooveremote from the axial grooves, and each fourth axial groove joins thefirst annular groove, and the axial grooves on each side of each saidfourth axial groove joins the second annular groove, whilst bores in therotary slide connect theremaining axialgrooves with the third annulargroove. Since only each fourth axial groove has to be connected to thethird annulargroove, the bores required for this can be comfortablyprovided in the rotary slide.

With a distributing valve of this kind, it is also possible to reversethe direction of rotation by transposing the first and second unions.

The change over device may be manually actuated.

It may however also be operated automatically. For this purpose, thechange over device is preferably constituted by a three-way valve whichis actuated in dependence upon the drop in pressure in the machine. Ifthe pressure drop in an engine is reduced as a result of a decrease inload, the engine automatically switches over to another kind ofoperation which permits a higher speed with lower torque, and viceversa.

In this connexion, it is particularly advantageous if the three-wayvalve has a plunger which'in a first position connects a pressurepassage, and in the second position, a low-pressure passage to thechange over valve openings, and which can bemoved from one of itspositions to the other in dependence upon the pressure in a pressurechamber adjacent an end face of thevalve, from which chamber the pistoncan bedisplacedinto its other position, and if the pressure-chamber isconnectible to the first or second union by way of a control valve andin dependence upon the position of a piston displaceable by the pressuredrop in the machine, this piston overriding the associated valveopenings with a lost motion action. As a result of the lost motion, an

upper pressure limit is established at which the engine is switched tonormal speed from high speed, and a lower pressure limit established atwhich the engine is switched from normal speed to high speed.

In the above-described arrangement it is also possible to fit thecontrol valve in the interior of the plunger of the three-way valve.

The invention will now be described in greater detail by reference to anembodiment illustrated in the draw- FIG. contains two graphs showing howthe change over operation is dependent upon pressure. K

For the purpose of the following description, it is as sumed that themachine of the invention is operated as an engine. A pipe supplyingpressurized fluid is therefore connected to a first union 1, and adischarge pipe to a second union 2. The engine includes a toothed ring 3(the first toothed element) having seven teeth, and a toothed wheel 4having six teeth. Displacement chambers 5 are formed between the ringand the wheel.

A distributing valve 6 consists of a first part 7 connected to androtating with the toothed ring 3, and a second part 8 connected to androtating with the toothed wheel 4. The valve-part 7 contains seven valveopenings 9 which are evenly spaced around its periphery and each ofwhich is connectible by a passage 10 to a displacement chamber 5. Thesecond valve part 8 contains twelve openings 11 which are divided intothree groups a, b and c. Each fourth opening a is continuously connectedthrough pipes 12 to the'pressure side first union 1. The second group bconsists of openings on either side of the openings 11a. The valveopenings l-lb arecontinuously connected through pipes 13 to the secondunion 2. The third group 0 is formed by the remaining openings which areconnected through pipes 14 to a change over device 15. This change overdevice can occupy either of two positions. In the first position,openings of the group 0 are connected to the first union l.In the secondposition openings of the group c are connected to the second union 2.The change-over device is actuated by way of a pulse line 16 independence .upon the pressure-drop in the engine.

ln the position of the change over device as illustrated, the valve.openings 11c are connected on the pressure side. They then act in thesame manner as the valve openings 11a. This results in a machine of thiskind operating in the normal way. If however the change over device ismoved into its other position, only the valve openings lla are locatedon the pressure side, whereas all theother valve openings are connectedto the discharge side. Then, only the discharge chamber 5a, indicated byhatching in FIG. 1, is supplied with pressurized-fluid. Theinstantaneous point of rotation M of the toothed wheel 4 is near the toptooth. The fluid pressure obtaining in the chamber 5a therefore appliesto the toothed wheel 4 a force that is substantially at right angles tothe lever-arm that rotates the toothed wheel. Therefore, in contrast towhat would be the case with pressurized fluid in the neighbouringchambers, the fluid in chamber 5a is effective with full force for themoment of rotation. Irrespective of the particular position of thetoothed wheel 4 and of part 8 of the distributing valve, there is alwaysonly one displacement chamber 5a, filled with pressurized medium,present. This displacement chamber 5a also always occupies approximatelythe same position in relation to the instantaneous point of rotation Mof the toothed wheel. Tests'have shown that in a control system of thiskind the torque is approximately halved and the speed is raised toapproximately twice the value. Efficiency, which is normally 80 percentin a toothed wheel machine of this kind, only drops to approximately 75percent. The degree of irregularity rises from 4 percent to onlyapproximately 10 percent. This is due to the fact that the singleeffective chamber 5a undergoes the greatest change in volume for a givenextent of rotation of the toothed wheel, whereas the two adjacentchambers only change slightly.

It is clear that similar conditions will occur if the unions 1 and 2 aretransposed. Then, only one chamber is connected to the discharge pipe,whereas the other displacement chambers connected to the pressure sidepartially cancel each other out as regards their effect.

A practical arrangement is illustrated in FIGS. 2 to 4.

The working part of the machine, which is illustrated in FIG. 2, has ahousing 17 which is closed at the lefthand end by a cover plate 18, andat the other end is extended by a spacer 19, the toothed ring 3 and thecover plate 20. The various parts are interconnected by means of screwbolts 21. A main shaft 22, integral with the rotary slide 23, rotates inthe housing-The main shaft is connected to the toothed wheel 4 by auniversal joint shaft 24. For this purpose the universal-joint shaft 24has toothed heads which mesh with corresponding internal teeth in themain shaft 22 and the toothed wheel 4.

The housing 17 constitutes the first part 7, and the rotary shaft 23 thesecond part 8 of the distributing valve 6. the valve openings 9, whichare connectible to the displacement chambers 5 through the boredpassages 10 in the housing 17 and in the spacer 19, are thereforeprovided at the inner periphery of abore in the housing. The valveopenings 11, in the form of axial grooves, are formed on the peripheryof the rotary slide. A first annular groove 25 is located to the rightof the axial grooves 11 and is connected to a pipe 26. A second annulargroove 27 is located to the left of the axial grooves 11 and isconnected to a pipe 28. A third annular groove 29 is provided at thatside of the second annular groove 27 remote from the axial grooves 11,and is connected to a pipe 30. Bores 31 lead from the annular groove 29to the axial grooves 1l of group 0. As shown in FIG. 3, the axialgrooves 11 of group a are extended to the annular groove 25, whereas theaxial grooves 11 of group b are extended to the annular groove 27. Theaxial grooves 11 of group c are spaced from the two annular grooves 25and 27, and only communicate with the annular groove 29.

FIGS. 2 and 4 together illustrate a complete machine. FIG. 4 illustratesa form of the change-over device 15. This device has an outer casing 32in which is inserted a sleeve 33 held at each of its ends by a plug 34and 35. The sleeve accommodates a displaceable plunger 36, in which agoove 37 enables an outlet opening 38, connected to the pipe 14, to beselectibly connected to an inlet chamber 39 or an inlet chamber 40. Theinlet chamber 39 is connected to the pipes 12 and 13 by way of a pipe 41and non-return valves 42 and 43 respectively which open towards thechamber 39. The higher pressure therefore always obtains in the inletchamber 39 irrespective of whether the pressurized medium is suppliedthrough the union 1 or the union 2. The inlet chamber 40 is connected tothe pipes 12 and 13 by way of a pipe 44 and two non return valves 45 and46 respectively which close towards the inlet chamber 40. The dischargepressure therefore always obtains in the inlet chamber 40, irrespectiveof whether the discharge pipe is connected to the union 1 or the union2. A chamber 47 containing a compression spring 48 is provided at one ofthe ends of the plunger 36. The chamber 47 is connected to the pipe 44and is therefore under discharge pressure. At the opposite end of theplunger 36 is a pressure chamber49 to which the supply pressure or thedischarge pressure can be optionally admitted through a passage 50incorporating two valve openings 51 and 52. For this purpose there isprovided a control piston 53 which is displaceable in a bore of theplunger 36, thereby overcoming the force of a spring 54. The bore issealed by means of a resilient plug 55. The supply pressure obtains inthe chamber 56 as a result of its communicating with the pipe 41 by wayof the pipe 57, and the discharge pressure obtains in the chamber 58since it communicates with the inlet chamber 40. The piston 53 undergoeslost motion relatively to the valve openings 51 and 52,'so that when thepiston is displaced, one opening is only uncovered after the other hasbeen closed for some time.

This construction of change over valve leads to an automatic change inspeed during which the two working ranges overlap each other. In theupper graph in FIG. 5, pressure is plotted against time, whereas in thelower graph engine speed is plotted against time. If it is assumed thatthe engine is initially running at high speed and the change over valveis inthe position illustrated in FIG. 4, then as soon as thepredetermined pressure difference I is established, the control pistonis pushed so far to the left that the valve opening 52 is uncovered, andsupply pressure is admitted to the pressure chamber 49. The valveplunger 36 and thus the change over device therefore move into the otherend position. The engine then runs at the lower speed n,. The drop inpressure diminishes to a corresponding extent. If, upon further loadingof the engine, the pressure rises above the limit value P the conditionsdo not change. Loading can be continued up to the safety pressure P Thissafety pressure is set by means of a safety valve, not illustrated. Ifthe load now drops, the conditions remain unchanged until the pressuredrop falls below the level P,. During the fall in pressure the valveopening 52 will have been initially closed by the control piston 53, sothat there is no change in the conditions', some time later the valveopening 51 is uncovered, so that the pressurized fluid can escape fromthe pressure chamber 49 towards the discharge side, since the plunger 36is pressed to the right by the spring 48. The engine then runs again atthe initial speed 11,. This speed is maintained even if the drop inpressure falls below the value P Thus, the engine runs at normal speedwithin the pressure range A, and at high speed within the pressure rangeB, these two ranges overlapposed for the purpose of reversing thedirection of rotation, there is no change in the change-over device 15,

because of the presence of the non-return valves 42, 43, 45 and 46.Instead a change over still occurs when the predetermined differences inpressure are exceeded.

I claim:

1. Fluid pressure apparatus comprising a casing having inlet and outletports, said casing having a speed and load control port, chamber formingmeans for forming expanding and contractingchambers, a valve having afirst part with channels extending to said chambers, said valve having acontinuously rotatable second part with first and second sets ofalternately arranged passages, said first set of passages including somepassages in constant fluid communication with said inlet port and atleast one passage in constant fluid communication with said controlport, said second set of passages being in constant fluid communicationwith said outlet port said control port being in selective communicationwith either the inlet or outlet port.

2. Fluid pressure apparatus according to claim 1 wherein said secondvalve part is cylindrically shaped and has three axially spaced annularchannels for said first and second sets of passages, said annularchannels being respectively in constant flluid communication with saidinlet and outlet ports and said control port.

3. Fluid pressure apparatus according to claim 1 including a change overunit having a fluid supply inlet and a fluid exhaust outlet, said unithaving a control outlet connected to said corltrol port, said unithaving means for selectively and alternately connecting said controlport to said supply inlet and said exhaust outlet.

4. Fluid pressure apparatus according to claim 3 wherein said changeover unit is actuated in response to a pressure drop change across saidinlet and outlet ports.

5. Fluid pressure apparatus according to claim 1 wherein said chamberforming means includes an internally toothed ring member and acooperating externally toothed star member having fewer teeth than saidring member and being disposed eccentrically relative thereto.

6. Fluid pressure apparatus according to claim 5 wherein said starmember has an even number of teeth and the alternate ones of said firstset of valve passages are connected to said control port.

7. Fluid pressure apparatus according to claim 6 wherein said starmember has six teeth.

8. Fluid pressure apparatus according to claim 7 wherein every forth oneof said sets of passages is connected to said control port.

1. Fluid pressure apparatus comprising a casing having inlet and outletports, said casing having a speed and load control port, chamber formingmeans for forming expanding and contracting chambers, a valve having afirst part with channels extending to said chambers, said valve having acontinuously rotatable second part with first and second sets ofalternately arranged passages, said first set of passages including somepassages in constant fluid communication with said inlet port and atleast one passage in constant fluid communication with said controlport, said second set of passages being in constant fluid communicationwith said outlet port said control port being in selective communicationwith either the inlet or outlet port.
 2. Fluid pressure apparatusaccording to claim 1 wherein said second valve part is cylindricallyshaped and has three axially spaced annular channels for said first andsecond sets of passages, said annular channels being respectively inconstant fluid communication with said inlet and outlet ports and saidcontrol port.
 3. Fluid pressure apparatus according to claim 1 includinga change over unit having a fluid supply inlet and a fluid exhaustoutlet, said unit having a control outlet connected to said controlport, said unit having means for selectively and alternately connectingsaid control port to said supply inlet and said exhaust outlet.
 4. Fluidpressure apparatus according to claim 3 wherein said change over unit isactuated in response to a pressure drop change across said inlet andoutlet ports.
 5. Fluid pressure apparatus according to claim 1 whereinsaid chamber forming means includes an internally toothed ring memberand a cooperating externally toothed star member having fewer teeth thansaid ring member and being disposed eccentrically relative thereto. 6.Fluid pressure apparatus according to claim 5 wherein said star memberhas an even number of teeth and the alternate ones of said first set ofvalve passages are connected to said control port.
 7. Fluid pressureapparatus according to claim 6 wherein said star member has six teeth.8. Fluid pressure apparatus according to claim 7 wherein every forth oneof said sets of passages is connected to said control port.